Banking transactions carried out in the uncertain conditions of mobile commerce involve highlevels of perceived risk and require substantial levels of trust. Therefore, gaining customer trust and reducing the influence of risk is imperative to developing and nurturing long-lasting and strong relationship between customers and retail banks. However, limited research is currently investigating the effects of overall perceived risk and trust on retail banking customers use of mobile commerce, particularly from the perspective of emerging African economies. This study investigates the effects of perceived risk and institution-based trust on the use of mobile banking apps among South African retail bank customers. The model was tested using responses obtained from 352 users of the mobile banking services of the five major retail banks (ABSA, Capitec, FNB, Nedbank, and Standard Bank) in South Africa. The findings of this study suggest that institution- based trust has a significant positive influence on use behaviour of mobile banking apps. Furthermore, perceived risk has a significant negative influence on use behaviour; and, lastly, institution-based trust is found to have a significant negative influence on perceived risk.